Plural-conductor actuating unit



May 1930- M. R. HUTCHISON, JR

vPLURAL CONDUCTOR AGTUATING UNIT .-Filed July 1. 1927 AMPUFIER INVENTORF Miller We as fiulc/lisorzJh BY Q I ATTORNEY AMPLIFIER Patented May 20, 1930 UNITED STATES PATENT OFFICE KILLER REESE HUTCHISON, JR, OF MADISON, NEW JERSEY, ASSIG'NOR, BY MESNE ASSIGNMENTS, '10 ACOUSTIC 'ZPRODUGTS COMPANY, OF NEW YORK, N.'Y., A COR- POBATION OF DELAWARE PLUBAL-CONDUCTOR ACTUATING UNIT Application filed July 1, 1927. Serial no. 202,884.

This invention relatesto sound propagating devices of the type in which a mechanical diaphragm, actuated byan electromagnetic unit is employed for imparting vibrations t a fluid medium.

In devices of this character, it is desirable to produce sound waves of maximum amplitude in response to a given applied force, and also to provide a device which is 1 capable of substantially linear sound reproduction in order to avoid distortion of the propagated waves. The mechanical arrange- -ment for converting the electromagnetic energy into a displacement of the sounding boar must, therefore, be capable of operating in such manner that the displacement ofv the soundingboard is substantially proportional to the applied current.

In accordance with the present invention,

the electromagnetic unit is suspended between a fixed support and a movable part of the diaphragm and is caused to execute a movement parallel to the diaphragm. ThlS movement therefore producesan action sim- .ilar to that of a toggle joint, and enables a force to be exerted on the diaphragm considerably larger than that which is applied to the unit itself.

The Y invention further provides a coil carrying a current which is placed in a magnetic field. The force tending to displace the coil from its normal position is dependent upon the strength of the field and the strength of the current passing through the coil. Consequently by applying a voice current to either the coil or to the field windings, the coil will be caused to execute corresponding vibrations which are translated, b means of the toggle action above mentione into a displacement of the diaphragm for the propagation of sound waves.

In order to increase the force which may be exerted upon the coil by the magnetic field, a plurality of turns may be employed, and the opposite sides of the coil may be 1nserted between ole pieces which are sultably energized or exerting a force thereon in the same direction and causing lateral displacement of the coil as a who le. 1 The invention also consists 1n certain new and original features of constructionand.

combinations of and claimed.

Although the novel features which are believed to be characteristic of this invention parts hereinafter setforth will be specifically pointed out in the claim nection with the accompanying drawing forming a part thereof, in which like reference characters have been used to denote like parts in the various figures. Since such illustration is, however, primarily for purposes of, disclosure, it will be understood that the structure and the method of operation thereof may be modified in various respects without departing from the broad spirit and scope of the invention.

One embodiment of the invention has been shown for purposes of illustration in the accompanying drawing, in which Fig. 1 is an elevation of a sound propagating device constructed in accordance with this invention;

Fig. 2 is a section taken on the line 2-2 of i Fig. 1; and

Fig. 3 shows diagramatically a nmdification thereof in which the pulsating current is applied directly to'the coil.

In the following description and in the claim the various parts of the apparatus and details of the invention will be identified by specific names for convenience, but they are intended to be as generic in their application as the art will permit.

Referring to the drawings more in detail, and particularly to Figs. 1 and 2, a form of the invention is disclosed comprising an electromagnetic unit 10 including a pair of pole pieces 11 and a coil 12 of conducting wirecomprising a plurality of turns located in the magnetic field produced by said pole pieces. Windings 13 and 14 are emplo ed for energizing the magnetic circuit an producing a magnetic field between said pole pieces. Windings 13 may be energized by a suitable source of direct current 15 and winding 14 may be energized by the output ciirrent of 'audio frequency amplifier 16 or from any other source of current the variations of which are to be converted into sound waves. Pole pieces 11 are mounted upon fixed framework 20 by suitable supports 21 (Fig. 1) and coil 12 is suspended between fixed support 22 and an intermediate part of the diaphragm 23 as by connecting links 24 and 25-. Said.

connecting links may be attached to coil 12 by any sultable means as by clamps 27 WhlCh are adapted to surround said coil and are provided with clamp screws 23 for attaching the same to said connectingllnks. Diaphragm 23 may be supported in framework 30 from base member 20, bracing 31 being provided for strengthening purposes. Coil 12 may be energized by direct current y from source 32 by means of which current is caused to flow serially through the various turns thereof.

Coil 12 may preferably be formed of aluminum wire WlllCh may be un-insulated since aluminum oxide is formed upon exposure to the air, and provides a sufficient amount of insulation between the various turns to prevent breakdown in the ordinary range of Volta es which are employed. A coil of alummum is furthermore light and presents a minimum amount ofinertia, and consequently is capable of reproducing the desired.

vibrations without substantial distortion.

In the operation of this device a force will be exerted upon coil 12 tending to move said coil in a direction parallel to diaphragm 23, said force being dependent upon the strength of the current flowing through the coil, the number of turns, and the strength of the magnetic field; Each of these elements is constant with the exception of the strength of the magnetic field, which is produced by the combined effect of coils 13 and 14. Coil In the modification shown in Fig. 3, the

voice current from amplifier 16 is shown as applied to coil 12 While the strength of the magnetic field between poles 11 is maintained constant by battery 15. The operation will be similar to that described above in connection with Fig. 1. Various other modifications might be employed, the essential feature being to produce the varying force on coil 12 and utilize this force to cause displacement of diaphragm 23.

An electromagnetic unit constructed as above is capable of operating efiiciently in response to currents of small amplitudes and to eXert a comparatively large force on the diaphragm or soundingboard. The number of turns in coil 12 may be varied to produce the most satisfactory results. By constructing the coil of aluminum, the weight is maintained as low as possible, and a comparatively large number of turns may be employed without increasing the inertia of the device'to a prohibitive value. By utilizing the inherent qualities of the aluminum whereby an oxide is formed to produce insu'lation between .the various turns, the

weight of the entire assembly is reduced since it is unnecessary to employ additional insulation. 7 y

While certain novel features of the invention have been shown and described and are pointed out in the annexed claim, it will be understood that various omissions, substitutions and changes in the forms and details of the device illustrated and in its operation may be made by those skilled in the art without departing from the spirit of Signed at New York in the county of New York and State of New York.

' MILLER REESE HUTCHISON, Jr.

-.,said coil is extremely small, this force will i be substantially proportional to the force applied to coil 12. Diaphragm 23 therefore will have a substantially linear characteristic and will faithfully reproduce the appliedvibrations.

Since the force of said coil 12 is dependent upon the various features above enumerated, that is, the strength of the magnetic field,

* the number of turns in the coil and the our- 

